To attenuate the vibration and to isolate the payload from structural dynamics of the base, vibration isolators may be included in the structural system. One example of a passive-mass damping and isolation system is a three-parameter vibration isolator, manufactured by Honeywell, Inc. of Morristown, N.J. The D-STRUT® vibration isolator is a three-parameter vibration isolation system that mechanically acts like a first spring (KA) in parallel with a second spring (KB) in series with a damper (CA). The D-STRUT® vibration isolator is disclosed in U.S. Pat. No. 5,332,070 entitled “Three Parameter Viscous Damper and Isolator” to Davis et al. The D-STRUT® vibration isolator includes a hollow shaft and a piston that is configured to slidably move through the shaft. The piston includes a flange that extends radially from a midsection thereof. The flange has a top surface that is coupled to a first sealed bellows and a bottom surface that is coupled to a second sealed bellows. Each of the bellows has a chamber that is filled with fluid. Thus, when the piston moves axially through the shaft, fluid flows from one of the bellows chambers to the other.
An active-passive hybrid damping and isolation system may alternatively be used to damp the structural system. One example of such a system is the Hybrid D-STRUT® vibration isolator, manufactured by Honeywell, Inc. of Morristown, N.J. The Hybrid D-STRUT® vibration isolator includes the passive-mass damping mechanism of the passive D-STRUT® vibration isolator and an active enhancement mechanism. The active enhancement mechanism enhances the force dissipation of the passive damping mechanism and includes an actuator mechanism which has a voice coil actuator system (such as a Lorentz force actuator) that can be tuned to damp a desired vibration. The Hybrid D-STRUT® vibration isolator is disclosed in U.S. Pat. No. 6,003,849 entitled “Hybrid Isolator and Structural Control Actuator Strut” to Davis and Hyde.
Although the above-described vibration isolators are generally useful for damping vibrations in most circumstances, they may be improved. For example, currently-known passive-mass and/or active-passive hybrid damping and isolation systems may not operate as effectively as desired in environments in which the structural system may be subjected to low frequencies (e.g., less than 5 Hz). In particular, vibrations in these frequency ranges may have relatively high amplitudes (e.g., greater than 0.25 cm), and the vibration isolators may be limited to damp vibrations having low amplitudes. Thus, other types of isolators may be employed in addition to the aforementioned types of isolators, which may be undesirable in configurations in which space may be limited.
Accordingly, it is desirable to have a damping and isolation system that is capable of damping vibrations of low frequencies and high amplitudes. In addition, it is desirable for the improved damping and isolation system to be capable of being retrofit into existing systems. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.